Lecture 2- Vision

Question 1

Tetrachromats

Answer 1

ancestor of birds, reptiles, mammals and most fish

four kinds of cone cells to see different colours: red, green, blue and ultraviolet

Question 2

Dichromats

Answer 2

Mammals lists Two of the four kinds of cones

difficulty differentiating between red and green but better night vision.

Question 3

Trichromats

Answer 3

Humans and other mammals re-developed the ability to see reds and oranges

three kinds of cone cells.

Question 4

Phototransduction

Answer 4

process by which light energy produces graded receptor potentials.

Question 5

Photoreceptors

Answer 5

modified neurons that have their photoreceptive ends inserted into the pigmented layer of the retina.

Vulnerable to damage, destroyed by intense light

Question 6

Visual pigment (photopigment)

Answer 6

molecules that change shape when they absorb energy from photons of light.

Embedded in stacks of discs in rod and cone cells

Question 7

Why do rods increase sensitivity but make fuzzy images?

Answer 7

There are up to 50 rods on a single bipolar interneurons

Question 8

Why do cones makes image sharper?

Answer 8

Each cone gets its own connection to optic nerve

Question 9

How is photopigment made?

Answer 9

combining a light- absorbing molecule, retinal, with one of four different four opsin proteins

Question 10

Rhodopsin

Answer 10

Opsin in rod cells

Question 11

Cone opsins

Answer 11

absorb light within given range of wavelengths

named after the colours they absorb (blue, green, and red).

Question 12

Bleaching

Answer 12

Pigment breakdown

Retinal and opsin separate

Question 13

What do Photoreceptors do in the dark?

Answer 13

Slightly depolarized

Releases inhibitory neurotransmitter to bipolar cell

Cannot stimulate ganglion cell to fire

Question 14

What do Photoreceptors do in the light?

Answer 14

Hyperpolarized

Stops releasing inhibitory neurotransmitter

Bipolar cell can now release excitatory neurotransmitter to ganglion cell, sending action potential along optic nerve

Question 15

Light adaptation

Answer 15

occurs when we move from darkness into bright light.

rods and cones are strongly stimulated. Large amounts of pigments broken down instantaneously, producing glare.

Pupils constrict to reduce the amount of light reaching the retina.

Question 16

Dark adaptation

Answer 16

occurs when we go from a bright area into a dark one.

Cones don’t function in low intensity light, rods need time to be deactivated. Pupils dilate to maximize the amount of light reaching the retina.

Rhodopsin accumulates in dark, so retinal sensitivity starts to increase

Question 17

Visual perception

Answer 17

Retinal ganglion cells merge in back of eyeball
to become the optic nerve

crosses at the optic chiasma to become the optic tracts connected to the thalamus.

From there, optic radiations project to primary visual cortex in occipital lobe

Question 18

Lateral geniculate nucleus (of thalamus)

Answer 18

integrates visual information to emphasize cone vision and to begin processing depth perception.

Question 19

Primary visual cortex

Answer 19

maps retinal information onto the occipital lobe for further processing

Question 20

Ventral “what” stream

Answer 20

goes to the temporal lobes for memory and the limbic system for emotions.

Question 21

Dorsal “where/how” stream

Answer 21

goes to the occipital and parietal lobes to let you recognize what you’re looking at and how you can interact with it.

Question 22

Depth perception

Answer 22

created when the visual fields of each eye, which differ slightly, overlap.

The visual cortex fuses these slightly different images into a three- dimensional perception.